1. Field of the Invention
The present invention relates to a thermal recording material, and more particularly, to a thermal recording material utilizing a transparent support adapted for uses such as recording medical images and recording scanning electron microscope (SEM) output.
2. Description of the Related Art
Thermal recording methods have been recently expanding in various fields such as recording methods for facsimiles and printers, and methods for label printing in point of sale (POS) equipment. This expansion is due to features of thermal recording, which possess advantages such as (1) image development being unnecessary; (2) the quality of the recording being similar to plain paper when the support is paper; (3) being easy to handle; (4) high color development density; (5) the recording device being simple and inexpensive; and (6) being free of unwanted noise when recording.
Accordingly, in recent years transparent thermal recording materials have been developed, which can be directly recorded upon using a thermal head, for purposes such as forming multi-colored images, projecting images with an overhead projector (OHP), and, in application to medical imaging, for directly observing images on a light box. JP-A No. 63-265682 describes an example of such a thermal recording material, which includes, on a transparent support such as a polymer film, a recording layer formed by coating and drying a coating liquid in which a substantially colorless color developing component and a colorless color developing component, capable of developing color by reaction with the aforementioned color developing component, are dispersed in a fine particulate state in a binder, or in a state which one of the color developing components is contained in microcapsules while the other is dispersed and emulsified.
Also, JP-A No. 1-285832 proposes a thermal recording material in which an opaque protective layer is laminated on an outermost color developing unit layer on a surface of the support. The proposed thermal recording material has a structure including an opaque protective layer that enables a recording image to be observed as a reflective image from one side. Such a thermal recording material can improve the sharpness of the image.
However, the drawback of these thermal recording materials is that the image tends to be discolored by heat or light, and the storability of the image remains unsatisfactory.